1. Field of the Invention
The present invention relates to an image stripping member for reproducing an image recording medium with ease by stripping an image forming material from the image recording medium used in a thermal transfer system or an electrophotographic system or the like, and to an image stripping apparatus and an image stripping method using the image stripping member.
2. Description of the Related Art
Currently, the most commonly-used image recording medium is paper. In recent years, the importance of conservation of forest resources has been recognized because of global environmental issues, and it has become important to decrease the use of wood as the raw material of paper. As one approach to decrease the use of wood, waste paper (used paper) is not burned, but is again used as recycled paper. In the utilization of waste paper as recycled paper, however, there are still many problems to be solved.
For example, there exist the following problems in recycling waste paper: leakage of secret documents and secret data of enterprises and the like; time, labor, and transportation involved in classification and collection and the like; and storage space and management for collected waste paper and the like.
Moreover, in the recycling of waste paper, there arise other problems such as the following: fibers of pulp are shortened and the quality of recycled paper is thereby deteriorated since waste paper is decomposed to pulp and a deinking apparatus is required to remove unnecessary ink and the like in images, when virgin pulp is used and the like. There is a further problem that paper manufacturing systems for manufacturing paper from pulp are large-scale, complex and expensive. Therefore, reproduction of waste paper cannot be carried out in offices and homes with ease.
If collection by type of paper, transportation, storage, reproduction and the like are not performed efficiently, a large amount of energy is consumed in these steps, resulting in a large amount of CO2. Consequently, global warming, which is one global environmental problem, may be further accelerated.
On the other hand, from the viewpoint of decreasing the use of petroleum resources, it is important to recycle plastics and the like. Examples of recording members which use plastics as a raw material include films for OHPs (overhead projectors) used in lectures, readings of papers, conference presentations, and the like. In OHP films, a thin image receiving layer is provided on a surface of a transparent film to firmly fix an image forming material thereon. At present, it is difficult to remove only the image forming material from the OHP film without damaging the image receiving layer, so that many sheets of used OHP films are discarded as waste after the film is used only once.
In order to solve such problems, there have been proposed various methods and apparatuses for stripping images from image recording media such as papers, plastic films or the like which have only been used once, by use of an image stripping member and reproducing an image recording medium. Examples of methods and apparatuses in which an image on an image recording medium is removed by a physical means are disclosed in the publications described below.
Japanese Patent Application Laid-Open (JP-A) Nos. 1-297294, 2-55195, 4-64472 and the like disclose the following. An image recording medium and an image stripping member are used. The image recording medium is formed of a material into which the image forming material does not penetrate, or is surface-treated with a releasing material. The image stripping member has a surface which is formed of a thermoplastic resin, e.g., the same resin as the resin of the image forming material, or has a surface on which is applied an adhesive exhibiting adhesiveness at lower temperatures than these resins. The image recording medium on which an image is formed is heated, and the heated image recording medium and the image stripping member are brought into contact with each other so that the fused image forming material is transferred to the image stripping member. The image forming material is removed from the image stripping member after the image forming material has cooled. However, there are problems in that operation must be suspended until the image forming material is cooled in order to peel off the image forming material from the image stripping member, or plain papers for general use and OHP films which are not surface-treated with a releasing material cannot be used in order to prevent an image stripping apparatus becoming inoperable due to strong adhesion of the image recording medium to the image stripping member, with an adhesive or a fused resin on the surface of the image stripping member, such that the image recording material and the image stripping member cannot be separated by a finger or the like.
An image stripping method is disclosed in Japanese Patent Application Laid-Open (JP-A) No. 5-232737 in which a felt roller such as stainless wool is used as an image stripping member, an image forming material on a sheet of paper coated with a releasing agent is softened by heating, and thereafter, the sheet of paper and the image stripping member are brought into contact with each other and the image forming material is removed from the sheet of paper with the help of friction. However, since friction is employed, the image forming material is adhered by rubbing the image forming member against the sheet of paper during stripping. The image forming material adhered by rubbing to the paper remains on the paper, and the reproduced paper thus obtained cannot be put into practical use.
An image stripping method is disclosed in Japanese Patent Application Laid-Open (JP-A) No. 6-219068 in which an image forming material on a sheet of paper, which is surface-treated with a thermally modified material having releasability, is softened by heating and removed by an image stripping member whose surface is made of an adhesive material. However, as is described in Japanese Patent Application Laid-Open (JP-A) No. 1-267294, plain paper and OHP films cannot be used and the image forming material transferred to the image stripping member cannot sufficiently be removed from the image stripping member, so that image peelability markedly deteriorates by repeated usage.
An image stripping method is disclosed in Japanese Patent Application Laid-Open (JP-A) No. 6-208318 in which a sheet of paper on which an image is recorded is immersed in a solution containing a deinking agent such as a surfactant and the like to weaken adhesiveness between the paper and the image forming material. Thereafter, a rotary brush made of polymer fibers such as nylon, acrylic resin, polyester or the like, a textile belt (web), or a blade is pushed on the paper in the solution or a deinking agent is jetted on the sheet through a high pressure nozzle, so that the image is peeled from the paper. There is a further problem, however, in that a long time is required for the solution to penetrate into the paper and for the adhesiveness between the paper and the image forming material to thereby be sufficiently weakened. Further, the image forming material stripped in the solution is again adhered to the paper.
Image stripping methods are disclosed in Japanese Patent Application Laid-Open (JP-A) Nos. 6-250569, 6-250570, 6-266264, 6-273966, 6-289643 and 7-13383, in which an image recording medium is immersed in a solution containing a surfactant. Thereafter, an image stripping member having an outermost layer made of the same resin as that of the image forming material, or an image stripping member made of a resin having a solubility parameter (SP) the same as or similar to that of the resin of the image forming material, or an image stripping member whose outermost layer is made of a pressure sensitive adhesive or an adhesive, or a variety of adhesive tapes, is adhered to the paper while being heated, so that the image forming material is stripped.
In any of these methods, however, there is a problem in that image forming materials which have firmly adhered to receiving members, and image forming materials which have penetrated into the recesses and projections (surface irregularities) of receiving members, and color images with high image densities cause difficulty in that, even if a large quantity of a surfactant is used, it is difficult for the surfactant to sufficiently penetrate between the receiving member and the image forming material, and the surfactant accumulates on the image stripping member by repeated use. Adhesiveness between the image stripping member and the image forming material is thereby weakened, and image peelability is reduced. If an image stripping member with a strong adhesive layer is used or the process of immersing an image recording medium in a solution is omitted in order to prevent such a problem, it is hard to remove (clean) an image forming material from an image stripping member or the image forming material adheres to the image stripping member, so that there arises another problem in that the image stripping apparatus is inoperable.
A method is proposed in Japanese Patent Application Laid-Open (JP-A) No. 8-262937, in which a solution of a surfactant and the like is held on a receiving member on which an image has been recorded for the purpose of achieving both peelability and cleanability, and there is used a stripping material having portions with respectively different adhesive forces to an image forming material in regions corresponding to sizes of images.
However, in actual use, there arise problems in that it is hard to manufacture an image stripping member having portions with different adhesive forces in a controlled manner, and an image forming material adhered to a region of low adhesive force to the image forming material does not have a sufficient fixing property so that image stability deteriorates.
The present invention has been made in light of the above, and an object thereof is to provide an image stripping member which enables easy reproduction of an image recording medium in an office or home, which maintains good image peelability over a long time, and which is applicable to general image recording media, and to an image stripping apparatus and an image stripping method using the image stripping member.
As a result of intensive research on image stripping members with which image recording media can be reproduced with ease, the present inventors have found that the above-mentioned object can be achieved by using an image stripping member having both properties of affinity and releasability with respect to an image forming material, and by using an image stripping apparatus and an image stripping method using the image stripping member, and have achieved the present invention based on these findings.
The present invention provides an image stripping member, which is used for stripping an image forming material from an image recording medium by contacting the image forming material on the image recording medium, wherein a material forming a surface layer of the image stripping member has affinity and releasability with respect to the image recording material.
The material forming the surface layer may contain a releasing material and an affinitive material, or may contain a material having both releasability and affinity. When the surface layer contains a releasing material, the content thereof is preferably in a range of 5 to 80% by weight.
The image stripping member may be structured such that a plurality of holes each having a bottom may formed in the surface layer of the image stripping member, and a material having releasability with respect to the image recording material or a material having both releasability and affinity with respect to the image recording material may be filled in the holes.
The affinitive material may be a pressure sensitive adhesive or a thermally-fusible material. The melting point of the thermally-fusible material preferably is in the range from a temperature which is 20xc2x0 C. lower than the melting point of the image forming material to a temperature which is 50xc2x0 C. higher than the melting point of the image forming material. More preferably, the thermally-fusible material is the same resin as the resin included in the image forming material.
Further, the thermally-fusible material is preferably mixed with a releasing material homogeneously, and for the purpose of homogeneous mixing, a compatibilizing agent, which improves the compatibility between the thermally-fusible material and the releasing material, or a plasticizer, can be included in the material forming the surface layer.
The material forming the surface layer can contain a material having both releasability and affinity, which material preferably is a resin containing a component for imparting releasability. The content of the component for imparting releasability is preferably in the range of 7 to 25% by mol.
In order to improve contact between an image forming material and an image stripping member in conformity with the irregularity of the surface of the image recording medium, formed by the image forming material, fine particles can be included in the surface layer, or an elastic layer made of silicone rubber or the like can be inserted between a substrate of the image stripping member and the surface layer. Releasing materials used preferably are a silicon compound such as an organic silicon compound, silicone rubber, silicone resin, silicone oil or a mixture thereof.
The present invention also provides an image stripping apparatus comprising: an image stripping member having a surface layer having affinity and releasability with respect to an image recording material; an image stripping means for stripping the image forming material from an image recording medium by making the image stripping member contact the image forming material on the image recording medium and heating the image recording medium; and a removing means for removing, from said image stripping member, the image forming material which has been transferred to the image stripping member from the image recording medium.
The above image stripping apparatus may comprise reducing means for reducing adhesiveness between the image recording medium and the image forming material, and/or second applying means for applying a releasing material on the surface of the image recording medium.
The present invention also provides an image stripping method comprising the steps of: stripping an image forming material from an image recording medium by making an image stripping member contact the image forming material on the image recording medium and heating the image recording medium, the image stripping member having a surface layer having affinity and releasability with respect to an image recording material; and removing, from the image stripping member, the image forming material which has been transferred to the image stripping member from the image recording medium.
The image stripping method can further comprise the step of reducing adhesiveness between the image recording medium and the image forming material before the step of bringing the image stripping member into contact with the image forming material on the image recording medium.
In the step of reducing the adhesiveness, the adhesiveness between the image recording medium and the image forming material can be reduced by heating the image forming material on the image recording medium.
In addition, in the step of stripping, the image forming material on the image recording medium may be heated.
In an image stripping method of the present invention, a well known image recording medium can be used, but an image recording medium made of a material whose surface layer has releasability with respect to an image recording material is preferably used.
The following description uses an electrophotographic method as an example. In general, an electrostatic charge is uniformly applied to a surface of an electrophotographic photoreceptor, and thereafter the surface is subjected to exposure on the basis of image information obtained from an original to form an electrostatic latent image. Then, an image forming material (toner) is supplied to the electrostatic latent image of the photoreceptor from a developing device to make the electrostatic latent image a visible image. The visible image is transferred to an image recording medium, and finally, the image forming material is fixed on the image recording medium by heat, pressure or the like.
Therefore, it can easily be understood that, in the case where an image is fixed by heat on an image recording medium, the image forming material is fused by heating the image recording medium again and adhesiveness between the image recording medium and the image forming material is reduced, so that the image forming material is easily peeled off from the image recording medium. However, if plain paper is used as an image recording medium, an amount of image forming material remains on the surface of the paper only by the heating treatment, to the extent that characters or images can be recognized or identified by the human eye. This is because the image forming material is made of a material with high affinity with paper fibers for the purpose of improving fixability.
If an image stripping member made of a material having high affinity with an image forming material, for example, an image stripping member made of the same type of resin as that of the image forming material, is brought into contact with an image forming material on an image recording medium under a condition that the image forming material is fused, the image forming material is transferred to the image stripping member from the image recording medium, and the image recording material can thereby be removed from the image recording medium.
However, in a conventional image stripping member, an image forming material, which is transferred to an image stripping member from an image recording medium, is difficult to be stripped from an image stripping member having high affinity to the image forming material and the image forming material is heterogeneously overlaid on the image stripping member due to use over a long period of time, so that peelability is greatly reduced. On the other hand, according to the present invention, since the surface layer of the image stripping member is made of a material having affinity and releasability with respect to the image recording material, even an image forming material, which is transferred to the image stripping member from the image recording medium, is easily removed from the image stripping member. Therefore, the peelability of the initial stages can be maintained over a long period of time.
The material forming the surface layer of the image stripping member of the present invention is obtained by combining an affinitive material having a large adhesive force with respect to an image forming material and a releasing material having a small adhesive force with respect to the image forming material, the mixing ratio being arbitrarily changeable. In this way, the adhesive force with respect to the image forming material can be controlled with ease, and even the adhesive force with respect to plain paper or OHP films, which have large adhesive forces with respect to the image stripping member, can also be controlled. Therefore, even if plain paper or a generally used OHP film is fed to the image stripping apparatus of the present invention, unsatisfactory winding of a paper sheet or an OHP film to the stripping member, which has conventionally been problematic, is prevented, so that there is no need for distinguishing plain paper from recycled paper.